Apparatus and method for controlling regeneration in exhaust emission control device

ABSTRACT

A method and an apparatus for controlling regeneration of an exhaust emission control device in which a diesel particulate filter (DPF) may be installed at a back stage of a reducing agent supply apparatus may include measuring temperature of a front stage of the DPF at the time of supplying a reducing agent, comparing a temperature value measured at the front stage of the DPF with a temperature modeling value of the front stage of the DPF, and controlling the regeneration of the DPF by comparing a difference between the temperature value and the temperature modeling value with a reference variation.

CROSS-REFERENCE(S) TO RELATED APPLICATION

The present application claims priority of Korean Patent Application Number 10-2013-0157848 filed on Dec. 18, 2013, the entire contents of which application is incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a regeneration technology of an exhaust emission control device, and more particularly, to an apparatus and a method for controlling regeneration in an exhaust emission control device capable of stably performing DPF regeneration at the time of the DPF regeneration in an S-DPF system.

2. Description of Related Art

To cope with a tightening of exhaust regulations on passenger diesel car diesel, in particular, EURO6 and North American markets, it is essential to reduce NOx. In particular, in order for a passenger car to meet an exhaust regulation of the EURO6, there is a need to reduce NOx emission to about 56%, that is, NOx emission from 0.18 g/km which is the exhaust regulation of the existing EURO5 to 0.08 g/km.

To cope with the necessity of reduction in NOx, an exhaust emission control device called as lean NOx trap (LNT) or selective catalytic reduction (SCR) to purity NOx emitted from an engine has been developed or applied worldwide.

Among those, the SCR system, which is a method for purifying NOx by supplying a separate reducing agent (generally, urea) in front of an SCR catalyst, may be an exhaust emission control device having very large NOx purification efficiency without sacrificing fuel efficiency of a vehicle.

The SCR system has a configuration in which a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), a reducing agent supply apparatus, and an SCR catalyst are generally disposed at a back stage of an engine in order.

That is, when an appropriate quantity of reducing agent is injected into an exhaust pipe by estimating a concentration of NOx emitted at the time of an operation of the engine based on modeling or measuring the concentration of NOx using a sensor, the injected reducing agent serves to reduce and purify the NOx while reacting with the SCR catalyst.

Meanwhile, a passenger car diesel engine has excellent fuel efficiency but is expensive and an exhaust emission control device, and the like for reducing NOx is additionally required. Therefore, an exhaust emission control device having reduced material cost and weight which having high-efficiency NOx purification performance is required.

Therefore, to meet the demand, an S-DPF which is a combination of a function of the SCR catalyst with a function of the DPF, that is, a system in which the SCR catalyst is coated on the DPF has been researched.

However, since the S-DPF system in which the DPF is combined with the SCR has two functions, there are many technical problems to overcome.

Among these problems, in particular, a problem of a deterioration of the SCR catalyst at the time of active regeneration due to soot generated within the DPF which is due to heat generation at high temperature is to be overcome. Further, in injecting urea (hereinafter, referred to as a reducing agent) for purifying NOx to a front stage of the DPF, there is a difficulty in injecting the reducing agent at the time of the high-temperature active regeneration.

In other words, unlike the existing SCR system, the S-DPF system has a configuration in which the diesel oxidation catalyst (DOC), the reducing agent supply apparatus, and the S-DPF (filter in which the SCR catalyst is coated on the DPF) are disposed at the back stage of the engine in order. Here, the soot accumulated within the S-DPF also needs to be periodically combusted and regenerated, like a general DPF.

In particular, to meet the tightened exhaust regulation, there is a need to inject the reducing agent during the DPF regeneration so as to reduce NOx excessively generated at the time of the DPF regeneration.

However, since a larger quantity of NOx is emitted during the DPF regeneration than during the general driving, a larger quantity of reducing agent needs to be injected to regenerate the NOx during the DPF regeneration.

Here, an injection quantity of the reducing agent varies depending on a NOx quantity, temperature, and the like, in particular, a larger quantity of reducing agent is oxidized before the reducing agent reacts with the SCR catalyst due to the high temperature characteristic depending on the regeneration even though the reducing agent is injected at the time of the DPF regeneration and thus the reducing agent may not be used, and a larger quantity of reducing agent is injected due to a larger quantity of NOx.

However, when a larger quantity of reducing agent is injected at the time of the DPF regeneration, the injected reducing agent contacts a temperature sensor installed at the front stage of the DPF in the state of an aqueous solution, and thus a precise temperature value of the front stage of the DPF may be distorted.

That is, at the time of the regeneration of the DPF, a governor keeps a targeted regenerating target temperature using a temperature value measured by the temperature sensor at the front stage of the DPF. In the S-DPF system, a large quantity of injected reducing agent contacts the temperature sensor to temporarily reduce the temperature recognized by the temperature sensor. In this case, to adjust the target temperature in the ECU, an injection quantity of fuel is increased to adjust the temperature.

That is, the temperature of actual exhaust gas already reaches temperature which may be regenerated but an inlet temperature of the DPF is suddenly increased due to the temporary distortion of the temperature sensor, such that the DPF may be damaged and the temperature of the temperature sensor may be continuously distorted, thereby causing the incomplete regeneration.

The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing an apparatus and a method for controlling regeneration of an exhaust emission control device capable of stably regenerating DPF by removing a temperature distortion at a front stage of DPF at the time of injecting a reducing agent during DPF regeneration.

A method for controlling regeneration of an exhaust emission control device in which a diesel particulate filter (DPF) is installed at a back stage of a reducing agent supply apparatus, may include measuring temperature of a front stage of the DPF at a time of supplying a reducing agent by the reducing agent supply apparatus while regenerating the DPF, comparing a temperature value measured at the front stage of the DPF with a temperature modeling value of the front stage of the DPF depending on the regeneration of the DPF based on a map showing a relationship between the temperature value and the temperature modeling value, and controlling the regeneration of the DPF by comparing a difference between the temperature value and the temperature modeling value with a reference variation and selecting the temperature value or the temperature modeling value as the temperature of the front stage of the DPF depending on the difference.

In the controlling of the regeneration, when the difference between the temperature value and the temperature modeling value exceeds the reference variation, the DPF is regenerated based on the temperature modeling value.

In the controlling of the regeneration, when the difference between the temperature value and the temperature modeling value is equal to or less than the reference variation, the DPF is regenerated based on the temperature value.

The DPF is coated with a selective catalytic reduction (SCR) catalyst.

The front stage of the DPF is provided with a temperature sensor to measure the temperature of the front stage of the DPF.

In another aspect of the present invention, an apparatus for controlling regeneration of an exhaust emission control device, may include a temperature sensor configured to measure a temperature of a front stage of a diesel particulate filter (DPF), and a control unit configured to compare a temperature value measured at the front stage of the DPF with a temperature modeling value of the front stage of the DPF depending on an active regeneration of the DPF based on a map showing a relationship between the temperature value and the temperature modeling value and to control regeneration of the DPF by comparing a difference between the temperature value and the temperature modeling value with a reference variation at a time of supplying the reducing agent by a reducing agent supply apparatus while actively regenerating the DPF to select the temperature value or the temperature modeling value as the temperature of the front stage of the DPF depending on the difference, wherein in controlling of the regeneration, when the difference between the temperature value and the temperature modeling value exceeds the reference variation, the DPF is regenerated based on the temperature modeling value, and wherein in controlling of the regeneration, when the difference between the temperature value and the temperature modeling value is equal to or less than the reference variation, the DPF is regenerated based on the temperature value.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for describing a configuration of an S-DPF system according to an exemplary embodiment of the present invention.

FIG. 2 is a diagram for describing a method for controlling a control flow of a control method according to an exemplary embodiment of the present invention.

FIG. 3 is a diagram illustrating a temperature profile at the time of injecting a reducing agent during DPF regeneration according to the exemplary embodiment of the present invention.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a diagram for describing a configuration of a DPF system according to an exemplary embodiment of the present invention, FIG. 2 is a diagram for describing a method for controlling a control flow of a control method according to an exemplary embodiment of the present invention, and FIG. 3 is a diagram illustrating a temperature profile at the time of injecting a reducing agent during DPF regeneration according to the exemplary embodiment of the present invention.

Prior to describing a method for controlling regeneration of an exhaust emission control device according to an exemplary embodiment of the present invention, a configuration of an exhaust emission control device according to an exemplary embodiment of the present invention will be described.

Referring to FIG. 1, the exhaust emission control device according to the exemplary embodiment of the present invention is a DPF system and may have a configuration in which a DOC, a reducing agent supply apparatus 5, and a DPF 3 are disposed at a back stage of an engine 1 in order.

In this configuration, the DPF 3 may be an S-DPF which is formed by being coated with an SCR catalyst.

A method for controlling regeneration of an exhaust emission control device according to the exemplary embodiment of the present invention is configured to largely include measuring (S10), comparing (S20), and controlling regeneration (S30).

Describing in detail the exemplary embodiment of the present invention with reference to FIGS. 2 and 3, a method for controlling regeneration of an exhaust emission control device in which the DPF 3 is installed at a back stage of the reducing agent supply apparatus 5 includes: measuring temperature of a front stage of the DPF 3 at the time of supplying a reducing agent by the reducing agent supply apparatus 5 while actively regenerating the DPF 3 (S10), comparing a temperature value T1 measured at the front stage of the DPF 3 with a temperature modeling value T2 of the front stage of the DPF 3 depending on the regeneration of the DPF 3 based on a map showing the relationship between the temperature value T1 and the temperature modeling value T2 (S20), and controlling the regeneration of the DPF 3 by comparing a difference between the temperature value T1 and the temperature modeling value T2 with a reference variation ΔT to select the temperature value T1 or the temperature modeling value T2 as the temperature of the front stage of the DPF 3 depending on the difference (S30).

In this configuration, the DPF 3 may be the S-DPF coated with the SCR catalyst as described above. Further, a temperature sensor 7 is disposed at the front stage of the DPF 3 to be able to measure the temperature of the front stage of the DPF 3.

That is, during the driving of a vehicle, an active regeneration time is determined by monitoring regeneration related variables of the DPF 3 and estimating a soot quantity within the DPF 3 due to the variable. At the time of determining the active regeneration time, the active regeneration is performed while controlling post-fuel injection and air quantity and at the same time, a reducing agent (urea) is injected to the DPF 3 side through the reducing agent supply apparatus 5 to remove NOx.

In this case, the map showing the relationship of the temperature modeling value T2 of the front stage of the DPF3 depending on the active regeneration of the DPF 3 may be set in a control unit (ECU) 9 according to the exemplary embodiment of the present invention.

Therefore, the exemplary embodiment of the present invention calculates the difference between the temperature value T1 measured at the front stage of the DPF 3 and the temperature modeling value T2 at the time of supplying the reducing agent along with the active regeneration of the DPF 3. The temperature value T1 measured by the temperature sensor 7 is selected as the temperature of the front stage of the DPF 3 used to control the post-fuel injection quantity at the time of the active regeneration depending on the size of the calculated difference value or the temperature modeling value T2 is selected on the map and thus is used to control the fuel injection quantity.

Therefore, at the time of injecting the reducing agent during the regeneration of the DPF 3, the temperature distortion at the front stage of the DPF 3 due to the reducing agent is prevented, such that the post-fuel injection quantity depending on the regeneration of the DPF3 is precisely controlled, thereby increasing the regeneration efficiency of the DPF 3.

In particular, referring to FIG. 3, in the controlling of the regeneration (S30) according to the exemplary embodiment of the present invention, when the difference between the temperature value T1 and the temperature modeling value T2 exceeds the reference variation ΔT, the DPF 3 may be controlled to be actively regenerated based on the temperature modeling value T2.

Further, in the controlling of the regeneration (S30), when the difference between the temperature value T1 and the temperature modeling value T2 is equal to or less than the reference variation ΔT, the DPF 3 may be controlled to be actively regenerated based on the temperature value T1.

That is, at the time of injecting the reducing agent during the regeneration of the DPF 3, when the difference between the temperature value T1 measured by the temperature sensor 7 and the temperature modeling value T2 is larger than the reference variation ΔT, the post-fuel injection quantity is controlled based on the temperature modeling value T2 to prevent the serious temperature distortion at the front stage of the DPF 3 and when the difference between the temperature value T1 measured by the temperature sensor 7 and the temperature modeling value T2 is smaller than the reference variation ΔT, the temperature distortion at the front stage of the DPF 3 is relatively small, and thus the post-fuel injection quantity is controlled based on the actually measured temperature value T1.

Therefore, the sudden increase in temperature of the front stage of the DPF 3 may be prevented by preventing the signal distortion of the temperature sensor 7 at the front stage of the DPF 3, thereby preventing the DPF from being damaged, the regeneration efficiency of the DPF 3 may be increased by precisely controlling the temperature of the front stage of the DPF, and the fuel quantity during the regeneration may be reduced by precisely controlling the post-fuel injection quantity to improve the fuel efficiency.

Meanwhile, the apparatus for controlling regeneration of an exhaust emission control device according to the exemplary embodiment of the present invention is configure to largely include the temperature sensor 7 and the control unit 9.

In detail, the apparatus for controlling regeneration of an exhaust emission control device includes: the temperature sensor 7 configured to measure the temperature of the front stage of the DPF 3, and the control unit configured to compare the temperature value T1 measured at the front stage of the DPF 3 with the temperature modeling value T2 of the front stage of the DPF 3 depending on the active regeneration of the DPF 3 based on the map showing the relationship between the temperature value T1 and the temperature modeling value T2 and control the regeneration of the DPF 3 by comparing the difference between the temperature value T1 and the temperature modeling value T2 with the reference variation ΔT at the time of supplying the reducing agent by the reducing agent supply apparatus 5 while actively regenerating the DPF 3 to select the temperature value T1 or the temperature modeling value T2 as the temperature of the front stage of the DPF 3 depending on the difference.

According to the exemplary embodiments of the present invention, the sudden increase in temperature of the front stage of the DPF may be prevented by preventing the signal distortion of the temperature sensor at the front stage of the DPF at the time of injecting the reducing agent during the DPF regeneration, thereby preventing the DPF from being damaged, the regeneration efficiency of the DPF may be increased by precisely controlling the temperature of the front stage of the DPF, and the fuel quantity during the regeneration may be reduced by precisely controlling the post-fuel injection quantity to improve the fuel efficiency.

For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “inner” and “outer” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents. 

What is claimed is:
 1. A method for controlling regeneration of an exhaust emission control device in which a diesel particulate filter (DPF) is installed at a back stage of a reducing agent supply apparatus, the method comprising: measuring temperature of a front stage of the DPF at a time of supplying a reducing agent by the reducing agent supply apparatus while regenerating the DPF; comparing a temperature value measured at the front stage of the DPF with a temperature modeling value of the front stage of the DPF depending on the regeneration of the DPF based on a map showing a relationship between the temperature value and the temperature modeling value; and controlling the regeneration of the DPF by comparing a difference between the temperature value and the temperature modeling value with a reference variation and selecting the temperature value or the temperature modeling value as the temperature of the front stage of the DPF depending on the difference.
 2. The method of claim 1, wherein in the controlling of the regeneration, when the difference between the temperature value and the temperature modeling value exceeds the reference variation, the DPF is regenerated based on the temperature modeling value.
 3. The method of claim 1, wherein in the controlling of the regeneration, when the difference between the temperature value and the temperature modeling value is equal to or less than the reference variation, the DPF is regenerated based on the temperature value.
 4. The method of claim 1, wherein the DPF is coated with a selective catalytic reduction (SCR) catalyst.
 5. The method of claim 1, wherein the front stage of the DPF is provided with a temperature sensor to measure the temperature of the front stage of the DPF.
 6. An apparatus for controlling regeneration of an exhaust emission control device, comprising: a temperature sensor configured to measure a temperature of a front stage of a diesel particulate filter (DPF); and a control unit configured to compare a temperature value measured at the front stage of the DPF with a temperature modeling value of the front stage of the DPF depending on an active regeneration of the DPF based on a map showing a relationship between the temperature value and the temperature modeling value and to control regeneration of the DPF by comparing a difference between the temperature value and the temperature modeling value with a reference variation at a time of supplying the reducing agent by a reducing agent supply apparatus while actively regenerating the DPF to select the temperature value or the temperature modeling value as the temperature of the front stage of the DPF depending on the difference.
 7. The apparatus of claim 6, wherein in controlling of the regeneration, when the difference between the temperature value and the temperature modeling value exceeds the reference variation, the DPF is regenerated based on the temperature modeling value.
 8. The apparatus of claim 6, wherein in controlling of the regeneration, when the difference between the temperature value and the temperature modeling value is equal to or less than the reference variation, the DPF is regenerated based on the temperature value.
 9. The apparatus of claim 6, wherein the DPF is coated with a selective catalytic reduction (SCR) catalyst. 